NGC 3109

NGC 3109
NGC 3109 by GALEX (ultraviolet)
Observation data (J2000 epoch)
Constellation	Hydra
Right ascension	10h 03m 06.9s[1]
Declination	-26° 09′ 34″[1]
Redshift	403 ± 1 km/s[1]
Distance	4.3 ± 0.3 Mly (1.33 ± 0.08 Mpc)[2][3]
Type	SB(s)m[1]
Apparent dimensions (V)	19′.1 × 3′.7[1]
Apparent magnitude (V)	10.4[1]
Other designations
UGCA 194, PGC, 29128,[1] h 3221, GC 2003[4]
See also: Galaxy, List of galaxies

NGC 3109 is a small spiral or irregular galaxy around 4.2 Mly away in the direction of the constellation of Hydra. It is the most prominent member of a Local Group subgroup. NGC 3109 is believed to be tidally interacting with the dwarf elliptical galaxy, Antlia Dwarf.^[5] It was discovered by John Herschel on March 24, 1835 while he was in South Africa.^[4]

Size and morphology

NGC 3109 is classified as a Magellanic type irregular galaxy,^[6] but it may in fact be a small spiral galaxy. If it is a spiral galaxy, it would be the smallest in the Local Group.^[7] NGC 3109 has a mass of about 2.3×10⁹ times the mass of the Sun, of which 20% is in the form of neutral hydrogen.^[8] It is oriented edge-on from our point of view, and may contain a disk and a halo.^[7] The disk appears to be composed of stars of all ages, whereas the halo contains only very old and metal-poor stars.^[9] NGC 3109 does not appear to possess a galactic nucleus.^[8]

From measurements of the neutral atomic hydrogen in the galaxy, it has been found that the disk of NGC 3109 is warped. The warp has the same radial velocity as gas in the Antlia Dwarf galaxy, indicating that the two galaxies had a close encounter approximately one billion years ago.^[10]

Composition

Based on spectroscopy of red giants in NGC 3109, it is known that the galaxy has a low metallicity, similar to that to the Small Magellanic Cloud.^[11] It is one of the most metal-poor galaxies in the Local group.^[12] NGC 3109 seems to contain an unusually large number of planetary nebulae for its luminosity.^[13] It also contains a substantial amount of dark matter.^[14]

Location

NGC 3109 is located about 1.3 megaparsecs (4.2 Mly) away, in the constellation Hydra. This puts it at the very outskirts of the Local Group.^[11] Its membership of the Local Group has been challenged, because it seems to be receding faster than estimates of the Local Group's escape velocity.^[15] It is distant enough from the largest members of the Local Group that it has not been tidally influenced by them.^[12]

Notes

1. ^ ^{a b c d e f g} "NASA/IPAC Extragalactic Database". Results for NGC 3109. http://nedwww.ipac.caltech.edu/. Retrieved 2006-11-19. 
2. ^ I. D. Karachentsev, V. E. Karachentseva, W. K. Hutchmeier, D. I. Makarov (2004). "A Catalog of Neighboring Galaxies" (abstract). Astronomical Journal 127 (4): 2031–2068. Bibcode 2004AJ....127.2031K. doi:10.1086/382905. 
3. ^ Karachentsev, I. D.; Kashibadze, O. G. (2006). "Masses of the local group and of the M81 group estimated from distortions in the local velocity field". Astrophysics 49 (1): 3–18. Bibcode 2006Ap.....49....3K. doi:10.1007/s10511-006-0002-6. 
4. ^ ^{a b} Irregular Galaxy NGC 3109
5. ^ Grebel, Gallagher, Harbeck, p.7
6. ^ Aparicio, Antonio; Artemio Herrero, F. Sánchez (1998). Stellar astrophysics for the local group: VIII Canary Islands Winter School. University of Cambridge. pp. 286. ISBN 9780521632553. http://books.google.com/?id=3gn5hS2zIkcC&pg=PA286&dq=ngc+3109#v=onepage&q=ngc%203109&f=false. 
7. ^ ^{a b} Sauvage, Marc; Grażyna Stasińska, Daniel Schaerer (2002). The evolution of galaxies: II--basic building blocks, Volume 2. Kluwer Academic Publishers. pp. 123, 124. ISBN 9781402006227. http://books.google.com/?id=xAPX8UfT6qAC&pg=PA123&dq=ngc+3109#v=onepage&q=ngc%203109&f=false. 
8. ^ ^{a b} van den bergh, Sidney (2000). The galaxies of the Local Group. University of Cambridge. pp. 265. ISBN 9780521651813. http://books.google.com/?id=NfOwG3cyAGIC&pg=PA265&dq=ngc+3109#v=onepage&q=ngc%203109&f=false. 
9. ^ Hidalgo, Sebastian L.; et al (2008). "The Disc-Halo Structure of NGC 3109". The Astronomical Journal 136 (6): 2332. Bibcode 2008AJ....136.2332H. doi:10.1088/0004-6256/136/6/2332. http://iopscience.iop.org/1538-3881/136/6/2332. Retrieved 2010-09-24. 
10. ^ Barnes, D. G.; W. J. G. de Blok (August 2001). "On the Neutral Gas Content and Environment of NGC 3109 and the Antlia Dwarf Galaxy". The Astronomical Journal 122 (2): 825. arXiv:astro-ph/0107474. Bibcode 2001AJ....122..825B. doi:10.1086/321170. http://iopscience.iop.org/1538-3881/122/2/825. Retrieved 2010-09-24. 
11. ^ ^{a b} Evans, Chris; et al. "The ARAUCARIA Project - First Observations of Blue Supergiants in NGC 3109". http://www.eso.org/sci/publications/messenger/archive/no.126-dec06/messenger-no126-5-6.pdf. Retrieved 2010-09-24. 
12. ^ ^{a b} Pena, M.. "An interesting comparison between PNE and H II regions in NGC 3109 and NGC 6822". RevMexAA 35: 74–75. http://www.astroscu.unam.mx/rmaa/RMxAC..35/PDF/RMxAC..35_mpena.pdf. Retrieved 2010-09-24. 
13. ^ Richer, Michael G.; Marshall L. McCall (1992). "Planetary nebulae and H II regions in NGC 3109". The Astronomical Journal 103: 54–59. Bibcode 1992AJ....103...54R. doi:10.1086/116040. 
14. ^ Jobin, Marc; Carignan, Claude (1990). "The dark side of NGC 3109". The Astronomical Journal 100 (3): 648–662. Bibcode 1990AJ....100..648J. doi:10.1086/115548. 
15. ^ Plotner, Tammy (2009-05-18). "Turning the Tides – NGC 3109 by Ken Crawford". Universe Today. http://www.universetoday.com/27388/turning-the-tides-ngc-3109-by-ken-crawford/. Retrieved 2010-09-24. 

References

• Grebel, Gallagher, Harbeck (2003) The Progenitors of Dwarf Spheroidal Galaxies ArXiv.org. retrieved Nov. 2007

External links

• NGC 3109 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images

Coordinates: 10^h 03^m 06.9^s, −26° 09′ 34″